Wheel detectors are among the most common type of apparatus in use to detect a particular part of a railroad car, that is, a wheel, at a known fixed point along the right-of-way, in contrast to area detection or detection of the presence of the entire car by various forms of proximity detectors. Wheel detectors may be used, for example, for activation and/or timing of such wayside apparatus as weigh rails, hot box detectors, and highway grade crossing signals, and also in classification yards for car following and switch protection functions. A commonly used type of wheel detector is the electromagnetic type. These generally use two wire coils, i.e., a transmitter and a receiver, placed on opposite sides of the rail. The specific operation differs but usually the coil location and the alignment with the other coil and with the rail are critical. Such units require a wayside apparatus case away from the rails to house the power supply, processing apparatus, and other items. Such a separate case also protects the apparatus from the weather, vandalism, and wayside maintenance equipment, reduces the effects of rail current and voltage surges induced, for example, by lightning, and eliminates the effect of rail vibrations. However, advantages in installation and maintenance of the wheel detector apparatus and increased economy in cost and operation can be obtained by eliminating the wayside case and still avoiding the extraneous detection signals resulting from induced currents and voltages. A wheel detector unit and associated apparatus mounted on the rail as a single module, preferably encased in epoxy, increases the advantages. In other words, a simple transducer unit entirely mounted on the rail to sense each wheel, thus eliminating the requirement for coils and power supplies and the criticality of the alignment, would be an effective unit. A well known Hall effect element mounted to respond to the change in a magnetic flux field due to the presence of the wheel will serve these goals.
Accordingly, an object of my invention is an improved detector for railroad car wheels using a Hall effect element to detect the passage of each wheel along the track rail.
Another object of the invention is an apparatus arrangement including a permanent magnet and a Hall effect element for detecting passage of railroad car wheels at a specific location along the track rail.
A further object of my invention is wheel detector apparatus for railroads including a ceramic type permanent magnet and a Hall effect element, positioned within a pole-to-pole opening in the permanent magnet, to respond to change in the flux density caused by the passage of a car wheel.
Yet another object of the invention is a wheel detector for railroad car wheels mounted on the gauge side of the track rail and consisting of a Hall effect element, mounted above a pole-to-pole opening in a permanent magnet, which responds to the change in the magnet flux level upon the passage of a wheel flange to generate a wheel detection signal.
Other objects, features, and advantages of the invention will become apparent from the following specification and appended claims when taken in connection with the accompanying drawings.